From the viewpoints of organic solvent emission control, reduction of energy consumption in the production process, etc., curable resin compositions containing acrylate or methacrylate have become important techniques in various applications, such as adhesives, pressure-sensitive adhesives, coating agents, inks, sealing materials and potting materials. Particularly in the electric/electronic field, downsizing and weight-lightening of electric/electronic parts have progressed with development of digital technology, and also for the adhesives, the pressure-sensitive adhesives, the coating agents, the sealers, the inks, the sealing materials and the potting materials used for the parts, improvement in performance accompanying downsizing and film-thinning has been required.
For example, a production process for precision parts such as electric/electronic parts sometimes includes a step of heating a part to not lower than 200° C. (e.g., step of mounting an electric part on a substrate), and in such a step, non-occurrence of cracks and the like is required. Further, uses of electric/electronic parts are accompanied by generation of heat, and in order to relax a stress caused by thermal expansion of a substrate by means of a sealing layer, an adhesive layer or the like, the above materials are required to have not only flexibility but also sufficient strength against the long-term heat history. Moreover, the adhesives and the coating agents of optical materials are required to have high transparency.
As a process for producing a cured product satisfying such strength, transparency, etc., a technique relating to a curable resin composition in which methacrylate or acrylate has been compounded with a low-molecular weight diene-based polymer having a methacryloyl group or an acryloyl group is known (see, for example, patent literature 1 or patent literature 2).
Such a curable resin composition is a curable resin composition which is excellent in that a cured product having excellent flexibility, moistureproofness, waterproofness and transparency is obtained. However, the following have been sometimes required: the diene-based polymer should also have higher compatibility with various monomers capable of being contained in the curable resin composition, such as a (meth)acrylate monomer having relatively high polarity; the diene-based polymer should have excellent workability when it is mixed with a (meth)acrylate monomer; the composition should have a satisfactory curing rate when it is cured; and in addition, a cured product obtained from the composition should also have excellent mechanical properties derived from the modified liquid diene-based rubber. Further, the resulting cured product has been also sometimes required to have excellent adhesion to various materials.